Manufacture of shoe stiffeners



Patented Aug. 22, 1933 UNITED STATES MANUFACTURE OF SHOE STIFFENERS Stanley P. Lovell, Newton, Mass., assignor to Arden Box Toe Company, Water-town, Mass., a Corporation of Massachusetts No Drawing.

Application October 9, 1931 Serial No. 567,991

6 Claims.

This invention relates to the manufacture of shoe stifl'eners like those used at the toe end of a shoe. Shoe stifieners sometimes consist of a porous fibrous foundation containing a stiflening colloid soluble in a non-aqueous solvent which gelatinizes the colloid, so that when the stiffener blank is immersed in the solvent,

it is rendered limp and moldable thereby.

Heretofore, it has sometimes been the custom 10 to associate the colloid in precipitated or finely divided condition with the foundation so as to make for high porosity and absorbency in the stiffener blank. Thus, shoe stiffeners are sometimes prepared with precipitated or finely divided colloidal nitrocellulose as the stiffening agent. I am using the term nitrocellulose in its comprehensive sense to mean nitrocellulose, as such, or nitrocellulose compounded with camphor and other agents in the form of celluloid, The shoe stiffener being highly porous is amenable to peneration quickly by a nitrocellulose solvent which serves to gelatinize the nitrocellulose and thus to transform the stiffener into a limp and moldable condition, in which condition it is assembled with the shoe upper,

molded during the pulling over and lasting operation, and allowed to set in place. Indeed, the shoe stiffener may be so porous and absorbent as to take up freely 150%, or more, by weight, of gelatinizing solvent. The shoe stiffener is thereby converted into such a limp condition that it is flabby and diflicult to assemble properly with a shoe uppen. Moreover, the excess solvent tends to exude under last- 86 ing pressure from the blank and to soil the shoe upper and lining, and to stick to the last. Even the skiving of the ungelatinized-stiflener may present the dii'iiculty that when putthrough a skiving machine the marginal or edge por- 40 tions are irregularly skived. This is attributable to the tendency for the ungelatinized blank to buckle and to become misplaced in the skiving machine.

My invention is broadly centered about the use of a colloidal stiffening agent soluble in a non-aqueous solvent, but I shall now deal specifically with the use of nitrocellulose, which perhaps best typifies the class of colloidal stiilening agents to which my invention applies. In

accordance with my invention, a porous fibrous sheet is treated with a solution of nitrocellulose and is then dried. The dried sheet thus contains a continuous phase of nitrocellulose which is not readily penetrated by a gelatiniz- 5 ing solvent. Consequently, were the dried sheet put into shoe stiflener blanks and then treated with a gelatinizing solvent, there would be an undesirably long time lag in transforming the blanks to a sufliciently limp condition for molding. I have found that if the freshly dried sheet undergoes the action of a highly humid atmosphere, for instance an atmosphere of live steam, there is a promiscuous striation and pittingof the continuous phase of nitrocellulose and the generation of microscopic channels into which a gelatinizing medium can readily pass so as to gelatinize the nitrocellulose and thus to transform a blank cut from the sheet into the required limp and moldable condition in the desired short period of time. The fact is that the blank instantlytakes up only that amount of solvent necessary for\ gelatinization whereupon gelatinization ensues at a rate compatible with the maintenance of the blank in a non-flabby state while it is being assembled with the shoe upper and with molding into the desired shape. The ungelatinized blank is possessed of suflicient rigidity to permit of perfect skiving; and, although it quickly absorbs gelatinizing solvent, nevertheless it does not imbide so much solvent that there is danger of soiling the'shoe upper and lining and of sticking to the last during the shoemaking operations. It must be borne in mind that shoe stifieners containing nitrocellulose as the stiffening medium are often used in ladies shoes having delicate uppers, like snakeskin, kidskin, moire, satin, or the like. In such case one must guard against staining of the shoe upper, as is apt to take place when excess solvent is squeezed under lasting pressure from the stiffener.

Unless my invention is practised, a shoe stiffener carrying a continuous phase of nitrocellulose, after being dipped in a gelatinizing solvent, must be permitted to stand for some time in order to acquire the proper degree of limpness .and moldability to respond properly to shoemaking operations. Apart from the undesirability of a waiting interval, this sort of practice makes for variations in the results secured because there is the personal equation of correlating the time factor with the securement of the desired limpness and moldability in the stiffener blanks. By using stifieners made in accordance with my invention, the operator need only dip the blank in the gelatinizing solvent and then proceed at once to assemble the solvent-treated blank with the shoe upper and continue with shoemaking operations.

A specific example of procedure falling within the ambit of the present invention may be substantially as follows. A spongy or bibulous fabric of the nature of flannel is passed through a bath of celluloid dissolved in the suitable solvent, e. g., ethyl acetate. The celluloid solution may be of any suitable concentration, say, one prepared by dissolving about 20 parts by weight of suitably compounded celluloid in aboutl20 parts by weight of ethyl acetate. 'I'he fabricneed remain immersed .in this solution for only about one to two minutes to become saturated throughout with the solution. If desired, the celluloid solution may be applied to either or both faces of the fabric as by passing the fabric through a suitable coating or spreading machine. The coating or spreading operation need not necessarily produce a uniformly impregnated sheet, as the inside of the sheet may well be poorer in celluloid than the surfaces of the sheet, which may carry a pellicle of celluloid. When the fabric undergoes saturation by immersion in a bath of solution, it is preferable to remove excess solution from the fabric, as by scrapers or press rolls. The saturated or coated fabric is then dried in any suitable manner, as by passing over a bank of drying drums or through an atmosphere of heated air. The drying operation causes a setting of the celluloid as a continuous phase in the pores as well as on the surface of the fabric. Immediately after the dried fabric issues from the last drying drum or from the drying chamber, it is subjected to a highly humid atmosphere, preferably one furnished by steam at a temperature of, say, about 212 F. The freshly set'phase of nitrocellulose is characterized by its imperviousness, translucency and luster, but the steam transforms it into a lusterless opaque body having a promiscuously striated and pitted texture. While I cannot precisely account for the transformation which the nitrocellulose phase undergoes in the steaming atmosphere, nevertheless my picture is that inevitably there is associated with the freshly set phase of celluloid a certain amount of residual solvent, say 1% to 2%, and that the moisture quickly displaces the more volatile solvent to change the index of light refraction in the nitrocellulose phase. When the steam is released from the fabric as it emerges from the steaming chamber, there are microscopic fissures and pits left in the nitrocellulose phase even though the phase is still a continuous one.

The principles of the present invention extend to colloidal stiffening agents other than nitrocellulose, which are characterized by their ability to become gelatinized in non-aqueous solvents and which can be displaced by steam. The solvents preferably employed are highly volatile, that is have a boiling point below 212 F., but when the solvent has a boiling point in excess of 212 F., the steaming operation can be carried out at a temperature sufliciently high to effect the desired displacement of the solvent from the fabric by the steam. Included in the class of colloids falling within the purview of my invention, may be mentioned cellulose acetate and other cellulose derivatives. So, too, non-cellulosic materials of the nature of shellac, gum

dammar, and other resins, which are soluble in by charging the air with moisture in the form of a mist or fog as from spray nozzles. The dried fabric may require a longer period of contact with such an atmosphere than with a steamladen atmosphere to undergo the desired modifi- -phase of colloid having a promiscuously striated cation, but the moisture acts to disrupt locally the continuous phase of stiffening colloid, especially when the solvent employed for applying the colloid to the fabric is of a water-miscible variety so that its residiuum in the colloid phase permits of commingling with the moisture. The moisture or steam appears to modify largely the surface portion of the continuous phase of stiffening colloid, wherefore, rather than presenting a barrier to the gelatinizing solvent, the stiffening colloid phase has surface canals which permit the solvent to reach quickly its interior and to act at the very start on a large aggregate surface.

What I claim is: Y

1. A shoe stiffener comprising a bibulous flbrous foundation carrying a continuous phase of stiffening, water-insoluble colloid capable of being gelatinized by a non-aqueous solvent, said and pitted texture conducive to a rapid action of the gelatinizing solvent thereupon.

2. A shoe stiffener comprising a bibulous flbrous foundation carrying a continuous phase of nitrocellulose, said phase of nitrocellulose 0 having a promiscuously striated and pitted texture conducive to a rapid action of a nitrocellulose solvent thereupon.

3. In the manufacture of shoe stiifeners, those steps which comprise applying a non-aqueous solution of a stiffening, water-insoluble colloid to a bibulous fibrous foundation, drying said foundation to set the colloid as a continuous phase, exposing the dried foundation containing the freshly set phase of colloid to a highly humid 11. atmosphere to cause a striation and pitting of said phase, and cutting the foundation into shoe stiffeners.

4. In the manufacture of shoe stiffeners, those steps which comprise applying a solution of nitrocellulose to a bibulous fibrous foundation, drying said foundation to set the nitrocellulose as a continuous phase, exposing the dried foundation containing the freshly set phase of nitrocellulose to a steaming atmosphere to cause a striation and pitting of said phase, and'cutting the founto a steaming atmosphere to cause striation and pitting of said phase, and cutting the foundation into shoe stiffeners.

6. In the manufacture of shoe stiffeners, those steps which comprise applying a solution of nitrocellulose to bibulous fibrous foundation, drying said foundation to set the nitrocellulose as continuous phase, exposing the dried founda- \tion containing the freshly set phase of nitrocellulose to a steaming atmosphere at a temperature above the boiling point of the solvent used in the nitrocellulose solution, thereby causing a striation and pitting of said phase, and cutting the foundation into shoe stiffeners. H5

STANLEY P. LOVELL. 

